The bulb base size is typically indicated in the bulb's name and corresponds to the diameter of the base in eighths of an inch. Here's how to decipher it:
Understanding Bulb Naming Conventions
Bulb names generally follow a format like this: "A19," "PAR38," or "MR16." The letters indicate the shape of the bulb, and the number represents the diameter of the bulb (not necessarily the base itself, but closely related) at its widest point, measured in eighths of an inch.
Deciphering the Size
- The Number: The number in the bulb's designation indicates the diameter in eighths of an inch.
- Example: An A19 bulb means the bulb is an 'A' shape and its diameter is 19/8 inches, or 2.375 inches. This diameter is related to, but not exactly the base size itself, which is the part that screws into the lamp.
How This Relates to Base Size
While the number signifies the overall bulb diameter, this gives a general indication of the type of base the bulb has. Standard base sizes are usually paired with certain bulb shapes and diameters.
Identifying the Actual Base Size (E26, E12, etc.)
The above refers to the bulb's overall size. The base itself (the part that screws into the socket) is described using different nomenclature, such as E26 (standard medium base), E12 (candelabra base), etc.
To determine the actual base size (E26, E12, GU10 etc.), you can:
- Check the Bulb's Packaging: The packaging usually clearly states the base type (e.g., "E26 Medium Base").
- Look for Markings on the Bulb: Some bulbs have the base type printed directly on the base itself.
- Measure the Base: Measure the diameter of the screw base. This measurement (in millimeters) can be used to identify the base type using online conversion charts.
- Compare to Known Bulbs: Compare your bulb's base to other bulbs you know the base size of. For example, compare it to a standard incandescent bulb (which is usually E26).
Common Bulb Base Sizes
| Base Type | Description | Common Uses |
|---|---|---|
| E26 | Standard Medium Base (26mm diameter) | Table lamps, floor lamps, ceiling fixtures |
| E12 | Candelabra Base (12mm diameter) | Chandeliers, decorative lighting |
| E17 | Intermediate Base (17mm diameter) | Some appliance bulbs, smaller fixtures |
| E11 | Mini-Candelabra Base (11mm diameter) | Night Lights, Novelty Lights |
| GU10 | Twist and Lock Base | Recessed lighting, track lighting |
| MR16 | Multi-faceted Reflector, often bi-pin connections | Landscape lighting, accent lighting |
By understanding the naming conventions and knowing the common base sizes, you can accurately determine the correct bulb for your fixture.
